The laboratory mouse is the preeminent animal model system for investigation into the biology and genetics of human cancer. Mouse models have provided key insights into cancer susceptibility, the molecular genetics of tumor suppressor and oncogenes, and therapy response in pre-clinical and co-clinical studies. Human tumors engrafted into immune compromised and humanized mice (aka, Patient Derived Xenografts) are playing an increasingly important role in basic and translational cancer biology. The Mouse Tumor Biology (MTB) database is a unique on-line compendium of mouse models for human cancer. MTB provides electronic access to expertly curated information on diverse mouse models for human cancer along with tools for accessing and visualizing associated data from these models (http://tumor.informatics.jax.org). MTB integrates data from peer-reviewed literature and from direct submissions from researchers. Data in MTB are also obtained from other bioinformatics resources including PathBase, the Gene Expression Omnibus (GEO), and ArrayExpress. The MTB project team has a strong record of supporting the use of the mouse in basic cancer biology and genetics research by providing expertly curated data that facilitates the selection of appropriate strains of mice for cancer genetics research. In this proposal we describe our plans for the continued development of MTB with an emphasis on expanded support for mouse-human comparative cancer genomics and the use of the mouse in translational and pre-clinical work. The major goals for the project renewal include the following: *continue to populate MTB with data on strain-specific patterns of tumorigenesis in inbred, mutant, and genetically engineered mice, * incorporate new data types and develop new user interfaces for accessing information and data related to Patient Derived Xenograft (PDX) models of human cancer, develop new interfaces to support mouse-human comparative cancer genomics, and support the infrastructure of MTB and our user community through ongoing database maintenance, development of new software components, user support services, and community outreach activities.